docs: def curve_spline(x, y=None, weights=None, order=1, even_out=True,
                   smoothing=None, periodic=False, meta_data=None):
      '''
      curve_spline(coords) yields a bicubic spline function through
        the points in the given coordinate matrix.
      curve_spline(x, y) uses the coordinate matrix [x,y].
  
      The function returned by curve_spline() is f(t), defined on the
      interval from 0 to n-1 where n is the number of points in the
      coordinate matrix provided.
      
      The following options are accepted:
        * weights (None) the weights to use in smoothing.
        * smoothing (None) the amount to smooth the points.
        * order (3) the order of the polynomial used in the splines.
        * periodic (False) whether the points are periodic or not.
        * even_out (True) whether to even out the distances along
          the curve.
        * meta_data (None) an optional map of meta-data to give the
          spline representation.
      '''
      curv = CurveSpline(x,y, 
                         weights=weights, order=order,
                         smoothing=smoothing, periodic=periodic,
                         meta_data=meta_data)
      if even_out: curv = curv.even_out()
      return curv